Conventionally bio-oxidative techniques, such as bubbling air through contaminated water containing bacteria, have been used for digesting contaminants and for treating and purifying contaminated water such as sanitary waste water, drinking water and ground water. Bio-oxidative purification techniques occur slowly and require a large area footprint to treat significant volumes of water. These techniques also produce foul odors that affect neighboring property owners and generate large quantities of sludge as a byproduct. That sludge can be hazardous to human health and to the environment, containing heavy metals, toxins and bacteria that require further processing and treatment before the sludge can be hauled off site for disposal. The process is inherently energy-inefficient, since it requires continuously pumping volumes of atmospheric air into the treatment pools, most of which is nitrogen and therefore of no use to the oxidation process. Further, rates of bio-oxidation are sensitive to temperature and thus materially slower in colder weather. Thus, biooxidation suffers from a large footprint, long process time, foul odors, energy inefficiency, sludge disposal, and cost issues.
Non-biological processes for treating water have also been employed. Chemical treatment has included addition of coagulants, flocculants, adsorbants, filter aids and oxidants. Radiation from ultra-violet and nuclear sources, and physical treatments, such as air flotation, filtration, centrifuging, various types of osmosis, and ozone treatment have also been used. These approaches are expensive and time consuming and have not been widely adopted.
More recently electrolytic treatment of contaminated water has been proposed by Greenburg, et al. in U.S. Pat. No. 6,471,873 (“the '873 patent”), incorporated herein by reference. The '873 patent describes an electrolytic cell having an anode chamber and cathode chamber separated by a membrane of submicron porosity. An electric current is applied through the cell. Contaminated water is fed into the cathode chamber, then into a holding tank, and then into the anode chamber. At the cathode electrically driven reactions occur to bring about the agglomeration of colloidal particles which can then be filtered out. At the anode, high current densities facilitate the oxidation of ammonia to nitrogen gas and produce chloric acid to oxidize any residual soluble organic material and act germicidally. While the electrolytic treatment described in the '873 patent can be carried out on a smaller footprint, produce fewer odors, consume less energy, and greatly reduce sludge byproduct, further improvement is needed to reduce the amount of electricity used, extend the life of the electrodes, eliminate the production of chlorine gas, and reduce costs, and these improvements are provided by the present patent application.